What's the "een" in Halloween?
suffix representing "ten" in cardinal numbers that are multiples of ten (sixty, seventy, etc.), from Old English -tig, from a Germanic root (cf. Dutch -tig, Old Frisian -tich, Old Norse -tigr, Old High German -zug, German -zig) that existed as a distinct word in Gothic (tigjus) and Old Norse (tigir) meaning "tens, decades." Cf. tithe (n.).
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, according to one authority, is "perhaps due to contact with Babylonia."
suffix used in forming abstract nouns from adjectives (safety, surety, etc.), Middle English -tie, -te, from Old French -te, from Latin -tatem (nominative -tas, genitive -tatis), cognate with Greek -tes, Sanskrit -tati-. Also cf. -ity.