Jamieson, Fausset and Brown on 2 Timothy 1:16

16. The Lord give mercy--even as Onesiphorus had abounded in works of mercy.

the house of Onesiphorus--He himself was then absent from Ephesus, which accounts for the form of expression (2Ti 4:19). His household would hardly retain his name after the master was dead, as Bengel supposes him to have been. Nowhere has Paul prayers for the dead, which is fatal to the theory, favored by Alford also, that he was dead. God blesses not only the righteous man himself, but all his household.

my chain--Paul in the second, as in his first imprisonment, was bound by a chain to the soldier who guarded him.