All three words here (diôbolon, triôbolon, hêmiôbolion) are neuter nouns -- hence, presumably, the 'likewise' -- deriving from "obelos/obolos" (omicron 7), a weight or coin. When a coin, as here, there were six to the (Attic) drachma (cf. delta 1516). LSJ entry at web address 1.
For diw/bolon and triw/bolon see ?Aristotle, Athenaion Politeia 41.3 (web address 2: the first and second increases in pay, from 1 obol, for attending the assembly; 390s).
[1] The more authentic form is h(miwbe/lion. See generally LSJ s.v., and cf. alpha 2416, eta 345, eta 346, pi 752.