From dankwiki

iptables replaced ipchains in 2.4, which had replaced ipfwadm in 2.2. they have to some degree been replaced by nftables since 3.13 or so, which is likely to be replaced in turn by some eBPF-based method.

The term Xtables (also written as x_tables) refers to the iptables/ebtables/ip6tables family. nftables replaced the whole gang.