5 words for ACLSU 1-letter words

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1 letter (5)

a c l s u
Archaic object pronoun
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T
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H
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E
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E
Hint 1 meaning
The objective case of thou. See Thou.
Hint 2 anagram
ETHE
Hint 3 another clue
BEING USED OR WORKED FOR THE FIRST TIME
10 +2