Echidna denotes a snake, either an animal that emerges from a fire or a plural image used in hostile addresses.

The attested usage chiefly places the plural form in hostile addresses describing people as the offspring of vipers; a separate occurrence names a snake that comes out from the heat and fastens itself on Paul's hand.

1. Hostile “offspring of vipers” address · dominant

   The genitive plural form occurs in direct condemnatory addresses: in Luke 3:7 and Matthew 3:7 the APB renders the address “offspring of vipers” and asks who warned the hearers to flee coming wrath. In Matthew 12:34 the same address precedes a charge concerning evil speech, while Matthew 23:33 pairs “Serpents” with “offspring of vipers” and asks how the hearers will flee judgment.

   Luke 3:7Matthew 12:34Matthew 23:33Matthew 3:7
2. A snake encountered at the fire · rare

   In Acts 28:3, the nominative singular form identifies the creature that comes out from the heat after brushwood is placed on the fire; the APB says that it fastens itself on Paul's hand.

   Acts 28:3

In the Anselm Project Bible: The APB renders the singular occurrence in Acts 28:3 as “a snake,” while the plural occurrences appear within “offspring of vipers” and, in Matthew 23:33, alongside “Serpents.” These renderings show the clauses' presentation rather than a fixed English equivalent.