Mastering past tense: why "had did" doesn't quite work

What kind of error is it?

Grammatical error - Tense usage

Why do people make this mistake?

People often mistakenly combine different past tense forms when trying to emphasize a past action, leading to the incorrect use of "had did" instead of choosing a single appropriate past tense form.

What is correct?

The correct form is to use the past perfect tense "had done" or the simple past tense "did", depending on the context.