1560s, "engage (the attention of) beforehand, engross in advance of or to the exclusion of other things," from pre- "before" + occupy. Sense of "occupy before others" is attested from 1620s. Related: Preoccupied; preoccupying.
late 14c., "act of fastening with a bar," verbal noun from bar (v.). The meaning "exclusion" is from 1630s. As a preposition, "excepting, excluding," it is from late 15c. The schoolhouse prank of barring out the teacher was so called by 1728.
1803, of language, "exclusion of admixture of any kind," often pejorative, "scrupulous affectation of rigid purity," from French purisme (see purist + -ism). As a movement in painting and sculpture that rejected cubism and returned to representation of the physical object, by 1921, with a capital P-.
1620s, "exclusion, action of excluding" (a sense now obsolete), from Medieval Latin seclusionem (nominative seclusio), noun of action from past-participle stem of Latin secludere "to shut off, confine" (see seclude). The meaning "act or state of being shut out or keeping apart" is by 1784. Blount's "Glossographia" (1656) has seclusory (n.) "a place where any thing is shut up a part from another."
"a cutting off or casting out from communication, deprivation of communion or the privileges of intercourse," specifically the formal exclusion of a person from religious communion and privileges, mid-15c., from Late Latin excommunicationem (nominative excommunicatio), noun of action from past-participle stem of excommunicare "put out of the community," in Church Latin "to expel from communion," from ex "out" (see ex-) + communicare "to share, communicate," related to communis "common" (see common (adj.)).
also lock-out, "act of excluding from a place by locking it up," especially of management locking out workers in labor disputes (1854) but also in 19c. the exclusion of a teacher from the schoolhouse by his pupils as an act of protest. From the verbal phrase lock (someone) out, which is attested from mid-14c. in the sense "turn or keep out (of a place), bar the doors against" (see lock (v.) + out (adv.)).
1831, "act of becoming specialized," noun of action from specialize. Biological sense from 1862. In science and scientific education, "a direction of time and energies in one particular channel to the exclusion of others," by 1880.
If you peruse the people in the news
The people that the magazines refer to
You'll find that they are naturally soignée
The special ones that all of us defer to
They've each a trait that seems to state first raters
That separates them from the small potaters
["Specialization," lyrics by Sammy Cahn]