miscible (adj.)

also *meig-, Proto-Indo-European root meaning "to mix." 

It forms all or part of: admix; admixture; immiscible; mash; meddle; medley; melange; melee; mestizo; metis; miscegenation; miscellaneous; miscible; mix; mixo-; mixture; mustang; pell-mell; promiscuous.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit misrah "mixed;" Greek misgein, mignynai "to mix, mix up, mingle; to join, bring together; join (battle); make acquainted with;" Old Church Slavonic mešo, mesiti "to mix," Russian meshat, Lithuanian maišau, maišyti "to mix, mingle," Welsh mysgu "to mix." 

"incapable of being mixed" (as oil and water are), 1670s, from assimilated form of in- "not, opposite of" (see in- (1)) + miscible, from Latin miscere "to mix" (from PIE root *meik- "to mix").