lag 2 
(lăg)
(lăg)n.
1. A barrel stave.
2. A strip, as of wood, that forms a part of the covering for a cylindrical object.
tr.v. lagged, lag·ging, lags
To furnish or cover with lags.
[Probably of Scandinavian origin; akin to Swedish lagg; see leu- in the Appendix of Indo-European roots.]