Etymology From Middle English manerely, equivalent to manner + -ly.
1
Having good manners; polite.
Lucetta, as thou lov'st me, let me have / What thou think'st meet, and is most mannerly.c. 1590–1591 (date written), William Shakespeare, “The Two Gentlemen of Verona”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, →OCLC, (please specify the act number in uppercase Roman numerals, and the scene number in lowercase Roman numerals):
Tut, tut, here is a mannerly forbearance: / The truth appeares ſo naked on my ſide, / That any purblind eye may find it out.1591 (date written), William Shakespeare, “The First Part of Henry the Sixt”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, →OCLC, [Act II, scene iv], page 103, column 2:
1 more example
1861, Charlotte Yonge, The Young Step-Mother ...but Genevieve's laugh roused her again, partly because she thought it less mannerly than accorded with the girl's usual politeness.