word-forming element meaning "worship of," used as an element in native formations from 19c. (such as bardolatry), from Greek -latreia "worship, service paid to the gods, hired labor," related to latron (n.) "pay, hire," latris "servant, worshipper," from PIE *le- (1) "to get" (see larceny).
word-forming element used in World War II armed forces slang and after, meaning "crazed or frazzled from stress due to" the thing specified (as in bomb-happy (1942), flak-happy (1943), trigger-happy (1942). The model might have been slap-happy in pugilism from 1936 as a slang variant of "punch-drunk."
noun word-forming element, "that which is written or marked," from Greek gramma "that which is drawn; a picture, a drawing; that which is written, a character, an alphabet letter, written letter, piece of writing;" in plural, "letters," also "papers, documents of any kind," also "learning," from stem of graphein "to draw or write" (see -graphy). Some words with it are from Greek compounds, others are modern formations. Alternative -gramme is a French form.
From telegram (1850s) the element was abstracted by 1959 in candygram, a proprietary name in U.S., and thereafter put to wide use as a second element in forming new commercial words, such as Gorillagram (1979), stripagram (1981), and, ultimately, Instagram (2010). The construction violates Greek grammar, as an adverb could not properly form part of a compound noun. An earlier instance was the World War II armed services slang latrinogram "latrine rumor, barracks gossip" (1944).