"to furnish with battens," 1775, from batten (n.) "strip of wood, bar nailed across parallel boards to hold them together." Nautical phrase batten down "cover (hatches) with tarpaulin and nail it down with battens to make it secure" is recorded from 1821. Related: Battened; battening.
also door-nail, "large-headed nail used for studding batten doors for strength or ornament," late 14c.; see door (n.) + nail (n.). The figurative expression dead as a doornail is attested as early as the word itself.
But ich haue bote of mi bale bi a schort time, I am ded as dore-nail. ("William of Palerne," c. 1375).
Compare key-cold "lifeless, inanimate, devoid of heat, cold as a metal key" (1510s). Also in Middle English as a symbol of muteness (domb as a dor nail, c. 1400).