
Etymonline: -ty (1): “English ... retains traces of a base-12 number system” - peter_d_sherman
https://www.etymonline.com/word/-ty#etymonline_v_18884
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peter_d_sherman
>"English, like many other Germanic languages, _retains traces of a base-12
number system._ The most obvious instance is eleven and twelve which ought to
be the first two numbers of the "teens" series. Their Old English forms,
enleofan and twel(eo)f(an), are more transparent: "leave one" and "leave two."

Old English also had hund endleofantig for "110" and hund twelftig for "120."
One hundred was hund teantig. The -tig formation ran through 12 cycles, and
could have bequeathed us numbers _eleventy ( "110") and _twelfty ("120") had
it endured, but already during the Anglo-Saxon period it was being obscured.

Old Norse used hundrað for "120" and þusend for "1,200." Tvauhundrað was "240"
and þriuhundrað was "360." Older Germanic legal texts distinguished a "common
hundred" (100) from a "great hundred" (120). This duodecimal system is
"perhaps due to contact with Babylonia" [Lass, "Old English"]."

