As a word meaning "months," the word חדשים is used in Ber. 38:24 and then multiple locations after Sh'mot 12:2.
יְרָחִים appears in Sh'mot 2:2, then (possibly) in Dev 33:14 and twice in Iyov.
When they refer to "months" do they both refer to the same thing or is there a difference (in meaning or reference)? Why would these 3.5 instances choose Yerachim over Chodashim? I thought that maybe a yerach was a moon cycle (from whatever point the moon is at to the next instance of that same point) while a chodesh was based on the newness (so "new to new") but I have no basis for that.