A helpful list of antonyms with the same word length for your everyday variable names:
lo
/hi
up
/dn
rd
/wr
beg
/end
bid
/ask
fst
/snd
/lst
(first/second/last)lhs
/rhs
(left/right hand side)src
/dst
top
/mid
/bot
get
/set
old
/new
⁰min
/mid
/max
²new
/del
¹⁰add
/del
¹fix
/var
one
/any
/all
/non
/nil
yay
/nay
give
/take
head
/tail
less
/more
play
/stop
pred
/succ
prev
/curr
/next
²push
/pull
this
/that
⁰true
/fake
⁰yeah
/nope
east
/west
below
/above
fresh
/stale
north
/south
start
/pause
/break
⁰sugar
/spice
large
/small
lower
/upper
allow
/block
inner
/outer
include
/exclude
accept
/reject
permit
/refuse
permit
/forbid
permitted
/forbidden
create
/insert
/remove
/delete
⁰encode
/decode
/verify
source
/target
unique
/shared
primary
/counter
relative
/absolute
producer
/consumer
positive
/negative
increment
/decrement
permanent
/temporary
⁰ C++ keyword, cannot be used as an identifier
¹ Python keyword, cannot be used as an identifier
² Python builtin, should not be used as an unqualified identifier, but ok as member
get
/got
/gen
(gen
for generate)width
/depth
length
/height
OK
/NG
⁰this->
/other.
localhost
/127.0.0.1
😂
⁰ the "NG" initials are commonly used in Japan for "Not Good"