drain: [OE] The underlying meaning of drain seems to be ‘making dry’. It comes ultimately from *draug-, the same prehistoric Germanic base as produced English drought and dry, and in Old English it meant ‘strain through a cloth or similar porous medium’. There then follows a curious gap in the history of the word: there is no written record of its use between about 1000 AD and the end of the 14th century, and when it reemerged it began to give the first evidence of its main modern meaning ‘draw off a liquid’. => drought, dry
drain (n.)
1550s, from drain (v.).
drain (v.)
Old English dreahnian "to drain, strain out," from Proto-Germanic *dreug-, source of drought, dry, giving the English word originally a sense of "make dry." Figurative meaning of "exhaust" is attested from 1650s. The word is not found in surviving texts between late Old English and the 1500s. Related: Drained; draining.