Origin: 1225–75;Middle English < Anglo-Frenchburgler (compare Anglo-Latinburg(u)lātor), perhaps < Old French*borgl(er) to plunder, pillage (< Gallo-Romance*būriculāre, equivalent to *būric(āre) (Old Low Franconian*būrj(an) to dart at, pounce upon + Vulgar Latin*-icāre v. suffix; compare Old Frenchburgier to strike, hit) + -ulāre v. suffix) + Anglo-French-er-er2; see -ar2
[C15: from Anglo-French burgler, from Medieval Latin burglātor, probably from burgāre to thieve, from Latin burgus castle, fortress, of Germanic origin]
1540s, shortened from M.E. burgulator, from Anglo-L. burglator (late 13c.), from O.Fr. burgeor "burglar," from M.L. burgator "burglar," from burgare "to break open, commit burglary," from L. burgus "fortress, castle," a Gmc. loan-word akin to borough. The intrusive -l- is
perhaps from influence of L. latro "thief," originally "hired servant." The native word was burgh-breche.