PIE *gal, bald, cf. calvinism, chauvinismから。さらにPIE *ghel, glowing, 語源的にはglass, gleamと同じ。
英語の語源
callow
callow: [OE] Old English calu meant ‘bald’. Eventually, the word came to be applied to young birds which as yet had no feathers, and by the late 16th century it had been extended metaphorically to any young inexperienced person or creature. It probably came, via West Germanic *kalwaz, from Latin calvus ‘bald’. => calvary
callow (adj.)
Old English calu "bare, bald," from Proto-Germanic *kalwa- (cognates: Middle Dutch calu, Dutch kaal, Old High German kalo, German Kahl), from PIE root *gal- (1) "bald, naked" (cognates: Russian golyi "smooth, bald"). From young birds with no feathers, meaning extended to any young inexperienced thing or creature (1570s). Apparently not related to Latin calvus "bald."
例文
1. He was a callow youth when he joined the newspaper.