†b.absol.to gain in: to get home, or to reach a place of refuge. Obsolete.
ΘΠ
the world > action or operation > safety > protection or defence > refuge or shelter > take or seek refuge [verb (intransitive)] > reach a refuge
to gain in1828
1828 J. S. SebrightObserv. Hawking (new ed.) 41 They must be found in an open country; and the wood, which is their place of retreat, must be so situated as to oblige them to fly against the wind to gain in.