My wife and I have reached the twelfth book in Patrick O’Brian’s Aubrey/Maturin series, The Letter of Marque, whose title reminds me of a Poul Anderson story, “Marque and Reprisal,” which I read as a teenage sf fan in my favorite magazine, F&SF (you can see the Jack Gaughan cover here), and which taught me the magnificent phrase letters of marque and reprisal (“commissions or warrants issued to someone to commit what would otherwise be acts of piracy”). If I had ever looked up the archaic-sounding marque, I couldn’t remember doing it, so I checked the OED, which has an entry updated in December 2000 with the following etymology:
< Anglo-Norman mark, marke, marque, merche and Middle French marche, marque, merque right of reprisal (1339; French marque) < Old Occitan marca right of reprisal, seizure by way of reprisal, object seized (12th cent.) < marcar to seize by way of reprisal (12th cent.), probably < a Germanic cognate of mark n.1 and mark v., the likely sense being ‘to mark as one’s own, to claim’, though this is uncertain and disputed. Compare post-classical Latin marca (1313 in a Gascon source), marcha (1152 in a document from Toulouse), marchia (1318 in a Gascon source), marqua (1293 in a British source), mercha (1295 in a British source) all denoting goods seized by way of reprisal; compare also Middle French merquer (1389), Catalan marcar (13th cent.), post-classical Latin marcare, marchare, marchiare, marquare (13th and 14th centuries in British and continental sources) to seize by way of reprisal.
Occurs frequently in the collocation marque and reprisal(s) after Anglo-Norman legal use, e.g.:
1353 Rolls of Parl. II. 250/1 Nous eions la Lei de mark & de reprisailles.
1417 Act 4 Hen. V Stat. 2 c. 7 Que de toutz attemptatz faitz par ses ennemys..encountre le tenure daucunes Trieuves..en les quelles nest pas fait expresse mencion que toutz marques & reprisailles cesseront..nostre Signior le Roi a toutz qi lour sentiront en tiel cas grevez, voet grauntier marque en due forme.
With letters of marque compare Anglo-Norman lettres merches (1435), Middle French lettre de marque (1549), post-classical Latin litterae marquae (1410 in a British source), litterae de marqua (14th–15th cent. in a British source).
More complicated than I would have thought, and reading Anglo-Norman legal verbiage always makes me smile.