Languages borrow words from other languages. This is called linguistic borrowing. Many English words are borrowed into ASL through fingerspelling.
Some words are spelled so frequently, that they become sign-like, in that they exhibit specific movements, locations or other word-like characteristics. This process is called lexicalization.
When fingerspelled loan signs become lexicalized, often specific processes can occur. Here are a few examples:
Sometimes, letters may be deleted. For example: often instead of fingerspelling the full phrase, M-I-C-H-I-G-A-N, native ASL users will sign M-I-C-H.
Sometimes, the sign will take on specific movements. For example, instead of fingerspelling the word J-O-B with each letter palm out, the signer may turn the last letter, B, inwards to form a more natural movement.
Sometimes, the phrase may be reduplicated. For example, instead of signing D-O, a person asking "what are you doing" might sign D-O-D-O-D-O etc.