encamp v.

word-forming element meaning "in; into," from French and Old French en-, from Latin in- "in, into" (from PIE root *en "in"). Typically assimilated before -p-, -b-, -m-, -l-, and -r-. Latin in- became en- in French, Spanish, Portuguese, but remained in- in Italian.

Also used with native and imported elements to form verbs from nouns and adjectives, with a sense "put in or on" (encircle), also "cause to be, make into" (endear), and used as an intensive (enclose). Spelling variants in French that were brought over into Middle English account for parallels such as ensure/insure, and most en- words in English had at one time or another a variant in in-, and vice versa.

1520s, "place where an army lodges temporarily," from French camp, in this sense from Italian campo, from Latin campus "open field, level space," especially "open space for military exercise" (see campus).

The direct descendant of Latin campus in French is champ "a field." The Latin word had been taken up in early West Germanic as *kampo-z and appeared originally in Old English as camp "contest, battle, fight, war." This word was obsolete by mid-15c.

Transferred to non-military senses by 1550s. The meaning "body of adherents of a doctrine or cause" is from 1871. Camp-follower "one who follows an army without being officially connected to it," such as sutlers, washer-women, etc., is attested from 1810. Camp-meeting "religious meeting for prayer, etc., held in an outdoor camp" is from 1809, American English, originally and especially in reference to Methodists. Camp-fever (1758) is any epidemic fever incident to life in a camp, especially typhus or typhoid. A camp-stool (1794) has a flexible seat and cross-legs and is made to be folded up and packed away when not in use.

1590s, "place where a camp is formed," from encamp + -ment. From 1680s as "act of forming a camp."