Why is ouster the act of ousting and not one who ousts?

ouster pronunciation   Dan ouster sdk

This video shows the #pronunciation of #oyster in British #English by three different voices

ouster pronunciation Pronunciation by ceruleanbill Male from United States Pronunciation by ceruleanbill User information  Pronunciation Dictionary

bestie malayalam short film OYSTER pronunciation • How to pronounce OYSTER 339 views · 3 years agomore language ouster - translation to Irish Gaelic and Irish Gaelic audio pronunciation of translations: See more in New English-Irish Dictionary from Foras na Gaeilge