E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
The standard borne before the Roman emperors. It consisted of a gilded spear, with an eagle on the top, while from a cross-staff hung a splendid purple streamer, with a gold fringe, adorned with precious stones. Constantine substituted a crown for the eagle, and inscribed in the midst the mysterious monogram. (See CONSTANTINES CROSS.) Rich (Antiquities, p. 361) says probably from the Gaulish lab, to raise; for Constantine was educated in Gaul. The Greek laba is a staff. (See Gibbon: Decline and Fall, etc. chap. xx.)