An Etymological Dictionary of Astronomy and Astrophysics

1. To unite or blend into a whole, as if by melting together. Related terms: → coalesce; → merge; → unify.
   

2. To combine or blend by melting together; melt (Dictionary.com).

Etymology (EN): From L. fusus “poured, melt, cast,” p.p. of fundere “to pour, melt.”

Etymology (PE): 1) Ividan, literally “to make (combine) into one entity,” from iv, → one, + -idan infinitive suffix.

2. Godâxtan “to melt,” from Mid.Pers. vitâxtan, vitâcitan “to melt,” from Av. vi-taxti- “flowing away, melting,” from vi- “apart, away from, out” (O.Pers. viy- “apart, away;” cf. Skt. vi- “apart, asunder, away, out;” L. vitare “to avoid, turn aside”) + tak- “to run, to flow,” taciāp- “flowing water,” tacinti (3pl.pers.act.) “to flow,”
   tacar- “course,” tacan “current, streaming;” Mod.Pers. tâz-, tâxtan “to run; to hasten; to assault,” tâzi “swift (greyhound),” tak “running, rush;”
   Mid.Pers. tâz-, tâxtan “to flow, to cause to walk,” tc- “to flow, to walk,” tag “running, attack,” tâzig “swift, fast;”
   Khotanese ttajs- “to flow, to walk;” cf. Skt. tak- “to rush, to hurry,” takti “runs;” O.Ir. tech- “to flow;” Lith. teketi “to walk, to flow;” O.C.S. tešti “to walk, to hurry;” Tokharian B cake “river;” PIE base *tek^w- “to run; to flow;” → flow.