"to pass the winter (in some place)," 1895, from over- + winter (v.). From 1933 as "to live through the winter;" transitive sense, in reference to animals, etc., "to keep alive over the winter" is by 1945. Related: Overwintered; overwintering. Old English had oferwintran "get through the winter."
Shackleton's men overwintered on Elephant Island
overweening
overweight
overwhelm
overwhelmed
overwind
overwinter
overwork
overwrite
overwrought
overzealous
ovi-