Twixt is also a English word meaning between. It is actually a contraction of betwixt (or sometimes atwixt, if you're feeling particularly archaic). It has existed in this contracted form for over 500 years, although it was oft written oddly, e.g., tuyx and tuix (English was very flexible in the 1500s).
Being a contraction, it is often written as 'twixt (Shakespeare may have been the first to use the modern apostrophized 'twixt). Modern dictionaries are split on the apostrophe issue, but the unadorned twixt seems to be slightly in the lead.
'Tis not a common word, but 'tis a good one.