quar·rel 2 
(kwôrəl, kwŏr-)
(kwôrəl, kwŏr-)n.
1. A bolt for a crossbow.
2. A tool, such as a stonemason's chisel, that has a squared head.
3. A small diamond-shaped or square pane of glass in a latticed window.
[Middle English quarel, from Old French, from Vulgar Latin *quadrellus, diminutive of Late Latin quadrus, square, from Latin quadrum; see kwetwer- in the Appendix of Indo-European roots.]