Sources

Pronunciation guide

(Main) gender: Female, can be male as well
Pronunciation: khee-ro–mʸee [çì.ɾó̞.mʲí]

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Etymology and/or ways to write:
The first element of this name stems from the adjective 広(廣)/弘/宏い (hiroi) meaning “spacious, vast, wide” (also 浩, 博, 裕, 紘, 絋, 拡). Other kanji which related to the adjective’s meanings include 寛 meaning “broadminded,” 大 meaning “big, large.” 洋 meaning “ocean, sea,” 悠 meaning “far off, distant,” 祐 meaning “help, assist,” 拓/啓 meaning “opening” and 光 meaning “light; ray, beam, glow.” A 2-kanji first element is possible, combining a hi kanji, like 比 or 妃, the latter meaning “princess,” and a ro kanji, e.g. 呂.
As for the second element, any mi kanji can be used, such as:

• 美 meaning “beauty”
• 実/實 meaning “seed; fruit”
• 海 meaning “sea, ocean”
• 未, referring to the sign of the Sheep or part of the word 未来 (mirai) meaning “future”
• 巳, referring to the sign of the Snake
• 己, referring to the 6th heavenly stem in Chinese calendar
• 見/視 meaning “looking, viewing”
• 弥 meaning “increase”
• 水 meaning “water”
• 三 meaning “three”
• 味 meaning “flavour, taste”

Mainly used on males, 大海 and 大洋, normally read as taikai and taiyō and both referring to the ocean, are also used for this name.

Popularity:
In use since at least the Meiji period (1868-1912), the type of usage in the early 20th century compared to what would occur later on was different, namely the level of usage (it was uncommon, peaking at around the 0.1% range) and who was being given the name more (it skewed heavily towards males, though female usage was slowly increasing).
Female usage of this name started to skyrocket in the 1940s and by the next decade, it was already within the top 50, being given to over 0.6% of baby girls born in that decade. Peak feminine usage happened in the 1960s with well over 2% of women born in that decade referring to this name, placing it within the top 5. Survey data from Dai-ichi Life via Tsunoda seems to concur with the peak usage statement with Hiromi ranking within the top 5 for 8 consecutive years from 1960 to 1967 (it was the top name in the survey for 1970 but did not show up again in the top 5 until 1975-7).
Feminine usage levels were dropping down by the 1970s, though percentages were still over 1% in the 1970s and most of the 1980s. Regarding male usage from the 1950s-1980s, it was still within the 0.1% range in the 1950s and 1960s, but it was already dropping down in popularity. By 1990, it was given to over 0.44% of girls and over 0.01% of boys, the name dropping out of the girls’ top 100 by 1992. Since the 2000s, it is a very uncommon to rare name for both genders.

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