Illustrated Companion to the Latin Dictionary/Labarum

This article incorporates text from a publication now in the public domain: Rich, Anthony (1849). The illustrated companion to the Latin dictionary, and Greek lexicon. p. vi. OCLC 894670115. https://archive.org/details/illustratedcompa00rich. 

LAB'ARUM. The imperial standard carried before the Roman emperors from the time of Constantine. In form it resembled the vexillum of the cavalry, consisting of a square sheet of silk attached by a cross bar to the shaft, richly ornamented with gold and embroidery, and emblazoned with the figure of a cross and a monogram of Christ (Prudent. in Symmach. i. 487.), as shown by the annexed example (Labarum/1.1), from a medal of Constantine. The name is probably formed from the Gaulish, lab, to raise; for Constantine was educated in Gaul.

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  Labarum/1.1