late 14c., "to lead, direct, conduct," from Old French guider "to guide, lead, conduct" (14c.), earlier guier, from Frankish *witan "show the way" or a similar Germanic source, from Proto-Germanic *witanan "to look after, guard, ascribe to, reproach" (source also of German weisen "to show, point out," Old English witan "to reproach," wite "fine, penalty"), from PIE root *weid- "to see." The form of the French word influenced by Old Provençal guidar (n.) "guide, leader," or Italian guidare, both from the same source. Related: Guided; guiding. Guided missile, one capable of altering course in flight, is from 1945.
mid-14c., "one who shows the way," from Old French guide, 14c., verbal noun from guider (see guide (v.)). In book titles from 1610s; meaning "book of information on local sites" is from 1759. In 18c. France, a "for Dummies" or "Idiot's Guide to" book would have been a guid' âne, literally "guide-ass." Guide-dog for the blind is from 1932.