-st1

1.
variant of -est1 :
first; least.

-st2

1.
variant of -est2 :
hadst; wouldst; dost.
British Dictionary definitions for -st

-est2

suffix
1.
forming the archaic second person singular present and past indicative tense of verbs: thou goest, thou hadst
Word Origin
Old English -est, -ast

-st

suffix
1.
a variant of -est2