βάπτισμα – baptizma “to baptize”: There are several references to sacred purification baths in Second Temple literature using the word ‘baptizo’. The word meant to dip or dunk something, like cloth in a dye bath, and from this it took on meanings like ‘washing’ and ‘cleaning’. Generally, when used as part of a sacred act of purification, the ‘dipping’ or washing that a person might undergo was something that they did privately, alone. You specifically don’t need another person to dip or wash or bathe in the water, so the fact that John was out there handing out the dippings was part of a larger message being delivered. 

The modern use of baptism is as a rite of initiation into Christianity. It’s possible that the original sense of use here in the story of John is that he was, like one dying fabric, converting the people of Judea to Roman culture.