Japanese Surname Igarashi 五十嵐

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came from, in Niigata Prefecture 新潟県 (on the north shore of Japan facing See of Japan),  a river 五十嵐川 that spelled (in English) and pronounced slightly differently: Ikarashi rather than Igarashi (which is the surname). The ja.wikipedia.org for the river (not surna,e) says it means: "五十嵐は、豊作をもたらす「五風十雨」を意味する。"

Japanese-English dictionary:
* go-jū  iso (ok), i (ok)   ５０; 五十 【ごじゅう[P]; いそ[ok]; い[ok]】 (num[eral]): "fifty; 50"
   ^ Yamamoto Isoroku 山本 五十六, where "iso" stands for fifty and roku is Chinese pronunciation for 六. (The "go" and "jū" are Chinese pronunciations for kanji 五 and 十, respectively.)
* motarasu もたらす 《齎す》 (vt): "to bring"
* arashi 嵐 【あらし】 (n): "storm; tempest"

Ikarashi or Igarashi literally means fifty storms.

My translation of "五十嵐は、豊作をもたらす「五風十雨」を意味する": Fifty Storms [the roiver name] brings abundant harvest/ bumoer crop, and means 五風十雨.

五風十雨. 漢典, undated
https://www.zdic.net/hant/%E4%BA%94%E9%A2%A8%E5%8D%81%E9%9B%A8
("語出漢·王充《論衡•是應》：'風不鳴條，雨不破塊，五日一風，十日一雨。'  謂五天颳一次風，十天下一場雨。後用以形容風調雨順。")