Is there an aorist in English grammar?

I’d argue there is. Aorist means “indefinite”, and was intended to mean “indefinite (unmarked) as to aspect”, which the Greek Aorist tense was, contrasting with both the Imperfect and the Perfect tense.

Tense naming conventions, however, are dependent on different grammatical traditions. Latin did not refer to aorists, and neither did Germanic grammars or Romance grammars; “simple past” is the term usual there.

Looking at Preterite – Wikipedia, I see that the English past “sometimes (but not always) expresses perfective aspect”. That would make it not so aorist. Then again, there were plenty of Classical Greek aorists that referred to completed actions—the aorist was the default tense, and you used the perfect only to emphasise that the action was completed.

So… yes, you can argue that the simple past is an aorist; but there’s no real point in changing the terminology of English grammar to say so.