early 13c., "characteristic attire of a religious or clerical order," from Old French habit, abit "clothing, (ecclesiastical) habit; conduct" (12c.), from Latin habitus "condition, demeanor, appearance, dress," originally past participle of habere "to have, hold, possess; wear; find oneself, be situated; consider, think, reason, have in mind; manage, keep," from PIE root *ghabh- "to give or receive."

Habit is a custom continued so steadily as to develop a tendency or inclination, physical or moral, to keep it up; as, the habit of early rising; the habit of smoking. Habit and practice apply more often to the acts of an individual; fashion and usage more often to many .... [Century Dictionary]

Meaning "clothing generally" is from late 14c. Meaning "customary practice, usual mode of action" is early 14c. Drug sense is from 1887. The Latin word was applied to both inner and outer states of being, and both senses were taken in English, though meaning of "dress" now is restricted to monks and nuns. In 19c. it also was used of the costume worn by women when riding on horseback.

"capable of being inhabited or dwelt in; suited to serve as an abode for human beings," late 14c., from Old French habitable "suitable for human dwelling" (14c.), from Latin habitabilis "that is fit to live in," from habitare "to live, inhabit, dwell," frequentative of habere "to have, to hold, possess" (from PIE root *ghabh- "to give or receive").

late 15c., "a dweller, a resident," from Old French habitant, abitant "inhabitant," from noun use of Latin habitantis, genitive plural of habitans, present participle of habitare "to live, inhabit, dwell," frequentative of habere "to have, to hold, possess" (from PIE root *ghabh- "to give or receive"). Specific meaning "a native Canadian of French descent" attested by 1789; it was the usual word for small farmers in 18c. Quebec, and Bartlett (1848) describes habitan as an Americanism for "The lower class of Canadians of French origin."

late 14c., "act or fact of dwelling;" also "place of lodging, abode," from Old French habitacion, abitacion "a dwelling; act of dwelling" (12c.) or directly from Latin habitationem (nominative habitatio) "a dwelling," noun of action from past-participle stem of habitare "to live, inhabit, dwell," frequentative of habere "to have, to hold, possess" (from PIE root *ghabh- "to give or receive").

mid-15c., "action of forming a habit; customary practice," from Medieval Latin habituationem (nominative habituatio), noun of action from past-participle stem of Late Latin habituare "to bring into a condition or habit of the body," from Latin habitus "condition, appearance, dress," originally past participle of habere "to have, hold, possess; wear; find oneself, be situated; consider, think, reason, have in mind; manage, keep" (from PIE root *ghabh- "to give or receive"). Meaning "condition of being habituated" is from 1816.

"customary manner, habit," c. 1400, from Old French habitude (14c.), from Latin habitudinem (nominative habitudo) "condition, appearance, habit," noun of state from past-participle stem of habere "have, hold; manage, keep" (from PIE root *ghabh- "to give or receive"). Related: Habitudinal (late 14c.).