RobH_en_tn/php/02/10.md

in the name of Jesus every knee should bend

Here "knee" is a synecdoche for the whole person, and bending the knee to kneel on the ground is a metonym for worship. "In the name of" here is a metonym for the person, telling who it is they will worship. Alternate translation: "every person will worship Jesus" (See: rc://en/ta/man/translate/figs-synecdoche and rc://en/ta/man/translate/figs-metonymy)

under the earth

Possible meanings are 1) the place where people go when they die or 2) the place where demons dwell.