"heard" as the past tense of "hear".

How did we get "heard" as the past tense of "hear"? Was it originally "heared" which then the "e" disappeared and the vowel shortened?

"hear" and "heard" come from Middle English "heren" & "herd(e)" from Old English "hieran" "hierde", so from Old English times the "d" was already connected to the stem.

Further back we find proto-Old English "hearian (hearjan)" & "hearida" where it is separated, but these forms are reconstructions and not attested forms.

And also we see that the same thing has happened in German.

"Hören" = to hear
"Gehört" = heard (past participle)