Because they were too inexperienced or low in rank for the cavalry, foot soldiers came to be called this
24 [PAR] They asked for a conference with Ormizda, and were induced by his promises .... 
and of royal rank, but when he came near they assailed him with insults and 
abuse, .... because of its low walls, had been abandoned by its Jewish 
inhabitants, was ... attended by a few light-armed soldiers and himself also 
marching on foot,... [DOC] [TLE] Battle Of Antietam | HistoryNet [PAR] The defenders were pushed out by dusk, at a cost of 2,500 Union casualties and 
3,800 ... called Dunkers because they practiced complete immersion in baptisms.