When Roland decided to make a subsidiary of itself dedicated to guitars in the early 1970s, they decided to call it MEG (Musical Engineering Group). Being the outward looking company that has been their mantra from day one, they realized Meg is a girls name in America and may dissuade buyers, many of them male, from buying their products. So they searched for a name that would connote power and mastership, and eventually came up with BOSS.
The earliest BOSS product was called B-100 The BOSS, released in 1974. This came with a clip-on pre-amp and a pickup to amplify acoustic guitars. At this point the BOSS company had not been formed and it was still technically a Roland product