Found in Sutra 1.12

The common meaning  of the term abhyāsa is “practice.” Etymologically, the term translates as “to place oneself well.” It is formed by adding the prefix abhi- to the verb ās (to place, to seat), then appending the suffix –a. The prefix abhi, like many prefixes has several meaning – “to, towards, greatly, excessively, very well “. The suffix a makes the verb to a noun, representing the action indicated by the verb. Thus the etymologically the word means placing oneself very well. The word has the common meaning ‘practice’. Typically etymological meaning, that is, based on the prefixes, suffixes and the verb provides an insight into the common or popular meaning. This meaning is one sees in a dictionary listing.