Where does “[[-tron]] ~ [[-tʰron]]” come from?

[[*-tron]] ~ [[*-tʰron]] (Proto-Hellenic) comes from Proto-Indo-European [[*-trom]] ~ [[*-dʰrom]].

Ancestry of “[[-tron]] ~ [[-tʰron]]”, step by step

Step	Language	Word	Meaning
1	Proto-Indo-European	[[-trom]] ~ [[-dʰrom]]	—

[[*-tron]] ~ [[*-tʰron]] — Etymology, Origin & Word History | Etymology Explorer