Blouse

1828, from French blouse ("a workman's or peasant's smock"), of obscure origin. Three theories include:

French blousse ("scraps of wool"), from Occitan lano blouso ("pure or short wool"), from blous, blos ("pure, empty, bare"), from Old High German blÅz ("") "naked, bare" (German bloss "bare")
A conflation of the aforementioned and French blaude, bliaud ("a kind of smock"), from Old French bliau, also from Frankish *blÄ«fald ("topcoat of scarlet colour"), from blÄ«- "coloured, bright" + -fald ("crease, fold"). More at blee, fold.
From Medieval Latin pelusia, from Pelusium, a city of Upper Egypt, a clothing manufacturer during the Middle Ages.

More at blee, fold.

Full definition of blouse

(plural blouses)

An outer garment, usually loose, that is similar to a shirt and reaches from the neck to the waist or below. Nowadays, in colloquial use, blouse refers almost always to a woman's shirt that buttons down the front.
(military) A loose-fitting uniform jacket.

1989, Bernard C. Nalty, Strength for the Fight: A History of Black Americans in the Military, page 311An anonymous black soldier summed up his feelings by declaring, "If I fail to blouse my boots, or I wear an Afro, I get socked. ..."