"clumsy, awkward; coarse," 1570s, from lubber (n.) + -ly (1).
Entries linking to lubberly
lubber n.
mid-14c., "big, clumsy, stupid fellow who lives in idleness," from lobre, earlier lobi "lazy lout," probably of Scandinavian origin (compare Swedish dialectal lubber "a plump, lazy fellow"). But OED suggests a possible connection with Old French lobeor "swindler, parasite," with sense altered by association with lob (n.) in the "bumpkin" sense. Sometimes also Lubbard (1580s), with pejorative suffix -ard.
Since 16c. mainly a sailors' word for those inept or inexperienced at sea (as in landlubber), but earliest attested use is of lazy monks (abbey-lubber). Compare also provincial English lubberwort, name of the mythical herb that produces laziness (1540s), Lubberland "imaginary land of plenty without work" (1590s).
-ly 1
suffix forming adjectives from nouns and meaning "having qualities of, of the form or nature of" (manly, lordly), "appropriate to, fitting, suited to" (bodily, earthly, daily); irregularly descended from Old English -lic, from Proto-Germanic *-liko- (Old Frisian -lik, Dutch -lijk, Old High German -lih, German -lich, Old Norse -ligr), related to *likom- "appearance, form" (Old English lich "corpse, body;" see lich, which is a cognate; see also like (adj.), with which it is identical).