The carmaker began in 1933 as part of Toyoda Automatic Loom Works, a sewing machine company founded by Sakichi Toyoda. When the auto unit was split off in 1937, son Kiichiro Toyoda decided to change  its name. The 3 reasons of name changes were tho followings:

1. Meaning: a Toyoda is a family name (ex. Sakichi Toyoda, Kiichiro Toyoda). They wanted to draw a line between company business and private affairs.
2. Sounds: Toyota is cleaner in pronunciation than Toyoda
3. Strokes:  when we write Toyota in Katakana it consists of 8 strokes. In Japan 8 is a lucky number. The shape of 8 in Chinese character represents large expectation to the future.