Your typo made me think you were asking specifically about ot. Looking back, I guess you meant to type 'it' not ot 'Just how ot is named'

OT, Occupational Therapy, explained above
PT, Physical Therapy, explained above
ST, Speech Therapy, works with verbal expressive skills, word finding, memory skills and more.

VT, Vestibular Therapy, works with balance issues
Behavioral/occupational psychology, helps one work with job tasks and job environments/relationships
NP, Neuro-Psychologist, looks at how the cognitive, memory, executive and motor functions are working.
NPA, NeuroPysch Assessment, testing system used by NP to measure the above functions.
Behavioral Optometry, looks at how the brain is focusing and converging the eyes and processing visual images

There are a few more therapy professions. Hopefully, others who have used them will post explanations.

A Physiatrist MD (Physical Medicine and Rehabilitation) is usually best at directing diagnostics and care to these various specialties. Family practice and neuro docs do not refer as often.