Correction (picky, picky, picky):   

Capotasto (no "r"), pronounced "KAH-poh-TAH-stoh" ("KAH-poh" for short). It's an Italian word. It means literally "head note," and at one time it referred to the nut of a lute, vihuela, guitar, or other similar instrument. Then along came the device that allowed the musician, in effect, to move the position of the nut. "Capotasto" then referred to the what might be considered the effective position of the nut. Later, it referred to the gizmo itself (as now).

The extraneous "r" (as in "capodastro") comes from a corruption I've seen in a few guitar manuals, and it undoubtedly comes from a mis-hearing of the word, usually spelled "capo de astro" (a mixture of Italian and Latin) which means "head of star," which makes no sense at all.

Cejilla, pronounced "say-HEE-yah." The Spanish word for Capo. "Ceja" means "eyebrow." The traditional wooden cejilla has a curved top, resembling an eyebrow, to accommodate the wooden tightening peg.

I'm a bit of a word-freak. Etymology, which includes word origins, has been a long-time interest of mine. Your mileage may vary.

Don Firth