early 15c., "one and indivisible, inseparable" (with reference to the Trinity), from Medieval Latin individualis, from Latin individuus "indivisible," from in- "not, opposite of" (see in- (1)) + dividuus "divisible," from dividere "divide" (see divide (v.)). Original sense now obsolete; the word was not common before c. 1600 and the 15c. example might be an outlier. Sense of "single, separate, of but one person or thing" is from 1610s; meaning "intended for one person" is from 1889.
Individual views a person as standing alone, or persons as standing separately before the mind: as, the rights of the individual; the rights of individuals: it is incorrect to use individual for person unemphatically ; as, there were several individuals in the room. [Century Dictionary]
"single object or thing," c. 1600, from individual (adj.). Meaning "a single human being" (as opposed to a group, etc.) is from 1640s. Colloquial sense of "person" is attested from 1742. Latin individuum as a noun meant "an atom, indivisible particle," and in Middle English individuum was used in sense of "individual member of a species" (early 15c.).