ur

fur

burr
were
her

urn

burn
turn
churn

earn

learn
fern
stern

fir

stir
sir
smirk

lurk

jerk
clerk
work

word

slurred
nerd
verb

urge

dirge
merge
splurge

worm

hurt
herd
bird

burp

slurp
chirp
Earp

Kirk

Dirk
yearn
Vern