A detailed answer is already here with an excellent explanation https://english.stackexchange.com/questions/40364/what-reasoning-is-behind-the-names-of-the-trigonometric-functions-sine-secan
A good researcher always double-checks multiple resources. One can never rely on one (history) source especially if it is open to editing by everyone. Wikipedia entry is quite incorrect which has nothing to with Indian, Persian transmission or Greek words. According to the unabridged Oxford Dictionary, the original definition of sine was "the length of a straight line drawn from one end of a circular arc parallel to the tangent at the other end, and terminated by the radius."
Here is the authentic etymology "< Latin sinus a bend, bay, etc.; also, the hanging fold of the upper part of a toga, the bosom of a garment, and hence used to render the synonymous Arabic jaib , applied in geometry as in sense 2"