Something that is anomalous is different from what is usual or expected. For years this anomalous behaviour has baffled scientists = unusual. different from what you expected to find (anomalus, from , , from an- + homalos )
[ &-'nä-m&-l&s ] (adjective.) 1655. Late Latin anomalus, from Greek anOmalos, literally, uneven, from a- + homalos even, from homos same; more at SAME.