Definition of rotmaster in US English:

rotmaster

noun

Military
rare, historical
  • The commander of a small detachment of soldiers.

Origin

Early 16th century; earliest use found in Remembrance Kynges Ordynance. Originally from either Dutch rotmeester (Middle Dutch rotmeester; from rot + meester) or its similarly-formed equivalent Middle Low German rōtemēster, with remodelling of the second element after master. In some forms probably directly from rot + master, after Dutch rotmeester, Middle Low German rotmēster, rotmeister, rōtemeister, and Swedish rotemästare (Old Swedish rotamästare; itself from Middle Low German); compare German Rottmeister. Compare later rot.