IPA: //rɪˈdʒɪstrɑːr//
KK: /rɪˈdʒɪstrɑr/
A person who is responsible for keeping official records, such as student enrollments or ownership of securities.
The registrar at the university helped me with my course registration.
Registrar → It is formed from "reg-" (from Latin "regere", meaning to rule or to direct) and "-istrar" (from Latin "registrare", meaning to record). The word "registrar" refers to a person who directs or oversees the recording of information, typically in an official capacity.
Think of someone who 'directs' ('reg-') the 'recording' ('-istrar') of important information — that's what a registrar does.
No commonly confused words.