英数

Probably a shortening of the longer term 英数字 (eisūji, “alphanumeric character”), itself a combination of 英字 (eiji, “alphabetic character, Latin letter”, literally “English character”) and 数字 (sūji, “number, numeric character”).

Alternatively, may be a compound of 英 (ei, “English”, here, in reference to the Latin alphabet used to write English) +‎ 数 (sū, “number; numeric”).

• IPA^(key): [e̞ːsɨᵝː]

英(えい)数(すう) • (eisū) 

1. (computing, input devices) alphanumerics, alphanumeric characters (as opposed to kana or kanji)

   英(えい)数(すう)は入(にゅう)力(りょく)できません。

   Eisū wa nyūryoku dekimasen.

   I cannot enter anything in alphanumerics.