A base or basis.
[Latin basis, base or pedestal, from Greek.]
In plants, growth or development that is basipetal (Latin petus, seeking) is towards the base or point of attachment; something basifixed is attached at or near the base. In medicine basioccipital refers to the base of the occiput, the back of the head; the adjective basilar refers to something situated at the base of a part of the body, especially of the skull, or of the organ of Corti in the ear. A basilect is a less prestigious dialect or variety of a particular language.
Basilisk and basilica, on the other hand, derive from Greek basileus, king.