late 14c., "a giving heed, active direction of the mind upon some object or topic," from Old French attencion and directly from Latin attentionem (nominative attentio) "attention, attentiveness," noun of action from past-participle stem of attendere "give heed to," literally "to stretch toward," from ad "to, toward" (see ad-) + tendere "stretch," from PIE root *ten- "to stretch."
Rare in English before 17c. Meaning "consideration, observant care" is from 1741; that of "civility, courtesy" is from 1752. Meaning "power of mental concentration" is from 1871. It is used with a remarkable diversity of verbs (pay, gather, attract, draw, call, etc.). As a military cautionary word before giving a command, it is attested from 1792. Attention span is from 1903 (earlier span of attention, 1892). Related: Attentions.