constable n.

title of nobility in some continental nations, corresponding to English earl, c. 1300, from Anglo-French counte "count, earl" (Old French conte), from Latin comitem (nominative comes) "companion, attendant," the Roman term for a provincial governor, from com "with" (see com-) + stem of ire "to go" (from PIE root *ei- "to go"). The term was used in Anglo-French to render Old English eorl, but the word was never truly naturalized and mainly was used with reference to foreign titles.

In ancient Rome and the Roman empire, [a comes was] a companion of or attendant upon a great person; hence, the title of an adjutant to a proconsul or the like, afterward specifically of the immediate personal counselors of the emperor, and finally of many high officers, the most important of whom were the prototypes of the medieval counts. [Century Dictionary]

early 13c., "building or enclosure where horses or cows are kept, building for domestic animals," from Old French stable, estable "a stable, stall" (Modern French étable), also applied to cowsheds and pigsties, from Latin stabulum "a stall, fold, aviary, beehive, lowly cottage, brothel, etc.," literally "a standing place," from PIE *ste-dhlo-, suffixed form of root *sta- "to stand, make or be firm."

Meaning "collection of horses belonging to one stable" is attested from 1570s; transferred sense of "group of fighters under same management" is from 1897; that of "group of prostitutes working for the same employer" is from 1937.

For what the grete Stiede

Is stole, thanne he taketh hiede,

And makth the stable dore fast.

[John Gower, "Confessio Amantis," 1390]