The Latin adjective canus, used primarily as a poetic word, meant ‘white,’ and in particular the Romans used it to describe the white hair of elderly people. The resulting Spanish cano has the same senses, and the feminine cana, now used as a noun, means ‘a white hair.’ The corresponding adjective canudo is ‘gray- or white-haired.’
The Spanish phrase peinar canas ‘to comb white hair’ is a metaphor for ‘to be old.’ English says that a picture is worth a thousand words, where thousand has the general sense ‘many.’ Spanish has the expression quitar [a alguien] mil canas, literally ‘to get rid of a thousand gray hairs.’ Because most people with gray hair wish they had less of it, the idiom means ‘to please, delight, cause joy.’ (Compare how English says “That takes a weight off my shoulders.”) According to the Diccionario de la Real Academia Española, in Peru and Uruguay the colorful expression sacar [a alguien] canas verdes means ‘to annoy, bother.’
Some sources trace Latin canus to Indo-European *kas-, which gave rise to English hare. The Germanic people would have named that animal after its grayish-white color.
© 2011 Steven Schwartzman