It's already a one-syllable name.
Famous people named Hart:
Actors Hart Denton and Hart Bochner; graphic novelist Hart Fisher; TV producer Hart Hanson; poet Harold Hart Crane; son of Miranda Kerr and Evan Spiegel, Hart Kerr Spiegel.
In medieval times, the word "hart" described red deer that were over five years old.
Fab Four-Letter Names For Boys, Handsome H Names For Baby Boys, Love-ly Names For February Babies, Simple One-Syllable Boy Names, Boy Names People Won’t Shorten, Short, Sweet Baby Boy Names, Celebrity Baby Names Of 2018,