The group of -ko (子) names that non-Japanese are most familiar with had been used most often in the 20th century. Nowadays, names that end in -ko only have one single preceding mora, the most popular being Riko.
On today’s name list post, we will be taking a look at some of the popular names ending in -ko that were popular in two different time periods: 1910-4 (end of Meiji period and start of Taishō period) and 1990-4 (start of Heisei period).
Let’s start with 1910-4:

1. Yoshiko – the first element of this name is usually derived from the classical adjective 良し/善し/好し (yoshi, modern yoi/ii) meaning “good, excellent, fine, nice, pleasant” with other kanji used for this name having either similar meanings, like 佳 and 美, or meanings with similar vibes to what the adjective means, such as 芳 meaning “fragrance” or 寿/壽 meaning “congratulations; longevity”
2. Masako – this next name was, at that time, most commonly written as 正 meaning “exact, precise,” owing to the fact that the Taishō period has arrived on July 30, 1912 and that period takes up around a half of the time frame referred here – other kanji used include 政 meaning “rule,” 昌 meaning “prosperous” and 賢 meaning “intelligence” (mostly stemming from 勝る/優る (masaru) meaning “to excel, surpass; to outweigh”
3. Fumiko – the first element of this name is usually written as 文 meaning “letter, writings,” though it can sometimes be written with two kanji, a fu kanji like 富/冨 meaning “riches, wealth, fortune” or 婦 meaning “(married) woman,” combined with a mi kanji, like 美 meaning “beauty”
4. Shi(d)zuko – for this next name, the first element is usually written as 静/靜 meaning “quiet, calm,” though it can be written with two kanji, a shi kanji, e.g. 志 meaning “will, aim, goal,” combined with a (t)su kanji, such as 津 meaning “harbour, haven” or 寿
5. Chiyoko – 千代 (or 千世), meaning “thousand years; forever,” is the most commonly used writing for the first element, though these kanji can be replaced with different ones, particularly 知/智 (chi) meaning “wisdom”
6. Haruko – this name would usually be written as 春 meaning “spring,” though there are other kanji used which are related or connotated to either 遥か/遙か (haruka) meaning “far off, distant” (e.g. 治 meaning “govern, manage”) or 晴れ (hare) meaning “clear/fine weather” (e.g. 朗 meaning “cheerful”)
7. Toshiko – for this last name of this bunch, it usually has three derivations: classical adjective 利し (toshi) meaning “sharp,” 敏し (toshi) meaning “keen, clever” (俊 has similar meanings to both), or 年/歳 (toshi) meaning “year; age” (寿/壽 is also used), though it can be written with 2 kanji, a to kanji, e.g. 登 meaning “ascent,” combined with a shi kanji, e.g. 志

Now, let’s take a look at 1990-4:

1. Yūko – for this first name of this part of the post, a yū kanji is most often used, such as 優 meaning “gentle, elegant; excellence, superiority,” 裕 meaning “abundant, rich,” 祐/佑/侑 meaning “help” or 由 meaning “reason, cause,” though it can also be suffixed with a kanji read as either u (e.g. 宇 meaning “eaves, roof”) or fu (e.g. 布 meaning “cloth”) and it can also be written as 木綿, referring to a string made from cut steamed and soaked mulberry bark fibres
2. Kanako – though single kanji are used for this name, such as 奏 meaning “playing music” or 叶 meaning “grant, answer,” a ka+na combination is the more prevalent way of writing this name – some of the common ka kanji include 加 meaning “addition,” 佳 meaning “beautiful, good” and 香 meaning “fragrance,” while common na kanji include 奈, 那 and 菜, the final one meaning “greens”
3. Momoko – this next name is usually written as 桃 meaning “peach” or, less commonly, 百 meaning “hundred,” though there are other writings used besides these two, such as 杏 (apricot via karamomo), 李 (Japanese/Chinese plum via sumomo) and 萌々, the kanji meaning “bud, sprout” with 々 used to repeat it
4. Shōko – for this next name, any kanji with the reading shō can be used, notably 翔 meaning “fly, soar,” 祥 meaning “blessedness, (good) omen” and 昌 meaning “prosperous”
5. Tomoko – the first element of this name is derived from 共 (tomo) meaning “together” (友/朋 meaning “friend” is an extension), though it is most often written as 智/知
6. Mariko – this next name is mostly written with a ma+ri combination, though several writings for the first element are taken from words, such as 真理 meaning “truth,” 万里 meaning “thousands of miles,” 茉莉, referring to the Arabian jasmine, or 鞠/毬 meaning “ball”
7. Yukiko – as far as single kanji go, it is usually written as 雪 meaning “snow” or 幸 meaning “good luck, happiness” (seemingly from the continuative form of the verb 行く (yuku) meaning “to go, reach, head (towards),” as seen in the word 御幸 (miyuki) which refers to an imperial outing), though more often than not, a yu+ki combination is more prevalent with ki kanji used including 紀/記 meaning “account, chronicle,” 希/稀, either meaning “rare” or part of 希望 (kibō) meaning “hope, wish, aspiration,” and 季 meaning “season”

What do you think? If you would like to add in your thoughts or other suggestions for this list, please share them in the comments below.