1952, in reference to a numeral system based on 16, not 10; from hexa- + decimal. From 1970 as a noun.
Entries linking to hexadecimal
hexa-
before vowels and in certain chemical compound words hex-, word-forming element meaning "six," from Greek hexa-, combining form of hex "six," from PIE root *sweks- (see six).
decimal adj.
c. 1600, "pertaining to a tenth or ten," from Medieval Latin decimalis "of tithes or tenths," from Latin decimus "tenth," from decem "ten" (from PIE root *dekm- "ten"). Applied to Arabic notation before modern use in reference to decimal fractions (fraction whose denominator is a power of 10) emerged 1610s. As a noun from 1640s, "a decimal fraction." Decimal point is by 1711; the use of the point seems to be due to Scottish mathematician John Napier, "Marvellous Merchiston," c. 1619.