late 14c., "a purpose, thing intended;" from aim (v.) or from nouns from the verb in Old French. The meaning "action of aiming" is from early 15c. To take aim originally was make aim (early 15c.).
c. 1300, "to estimate (number or size), calculate, count," senses now obsolete, from Old French aesmer, esmer (Old North French amer) "to value, rate; count, estimate," ultimately from Latin aestimare "appraise, determine the value of" (see esteem (v.)).
The meaning in English apparently developed from "calculate," to "calculate with a view to action, plan," then to "direct a missile, a blow, etc." (late 14c.). It also was used in Middle English of directing a letter, planting an altar, pitching a tent. The intransitive sense of "intend, attempt" (early 14c.) was used by Shakespeare but is now considered colloquial. Related: Aimed; aiming.
1520s, from French imitateur (14c.) or directly from Latin imitator "a copyist; a mimic," from imitari "to copy, imitate" (from PIE root *aim- "to copy").
1550s, from French imitable (16c.), from Latin imitabilis "that may be imitated," from imitari "to copy, portray" (from PIE root *aim- "to copy"). Related: Imitability.
c. 1400, "emulation; act of copying," from Old French imitacion, from Latin imitationem (nominative imitatio) "a copying, imitation," noun of action from past participle stem of imitari "to copy, portray, imitate," from PIE *im-eto-, from root *aim- "to copy." Meaning "an artificial likeness" is from c. 1600. As an adjective, from 1840.
"faculty of the mind which forms and manipulates images," mid-14c., ymaginacion, from Old French imaginacion "concept, mental picture; hallucination," from Latin imaginationem (nominative imaginatio) "imagination, a fancy," noun of action from past participle stem of imaginari "to form an image of, represent"), from imago "an image, a likeness," from stem of imitari "to copy, imitate" (from PIE root *aim- "to copy")
"final or adult stage of an insect," 1797, from Latin imago "an image, a likeness," from stem of imitari "to copy, imitate" (from PIE root *aim- "to copy"). "The name is due to the fact that such an insect, having passed through its larval stages, and having, as it were, cast off its mask or disguise, has become a true representation or image of its species." [Century Dictionary]