Etymology
Advertisement
acro- 

word-forming element meaning "highest, topmost, at the extremities," before vowels acr-, from Latinized form of Greek akro- "pertaining to an end, extreme," from akros "at the end, at the top, outermost; consummate, excellent" (from PIE *akri-, from root *ak- "be sharp, rise (out) to a point, pierce").

Related entries & more 
Advertisement
pico- 

word-forming element used in making names for very small units of measure, 1915 (formally adopted as a scientific prefix meaning "one trillionth" by the International System of Units, 1960), from Spanish pico "a little over, a small balance," literally "sharp point, beak," a word of Celtic origin (compare Gaulish beccus "beak").

Related entries & more