mid-15c., "to mold or cast from molten metal" (a sense now obsolete), from Latin conflatus, past participle of conflare "to blow up, kindle, light; bring together, compose," also "to melt together," literally "to blow together," from assimilated form of com "with, together" (see con-) + flare "to blow" (from PIE root *bhle- "to blow").
From c. 1600 as "to bring together from various sources." In reference to text, "to form by inadvertent combination of two readings of the same words," from 1885.