キュウ, ふる.い, もと
old times, old things, old friend, former, ex-
JLPT2 G5 S5 F549
萑 is 隹 short, squat bird + 艸 grass/plant (here acting as a shape indicator, suggesting the curvature of a pair of ears) → horned owl. 舊 adds 臼# (stooped) → owl (← bird of a stooped appearance) → *bent with rot* (compare 朽) → *old*; *former* → *old friend*.
[Full Kanji Etymology List]