log vs log up

log is a noun but log up is not a noun.

Word	Noun	Adjective	Verb	Adverb
log	Yes	No	Yes	No
log up	No	No	Yes	No

log (noun)	log up (noun)
measuring instrument that consists of a float that trails from a ship by a knotted line in order to measure the ship's speed through the water
a written record of events on a voyage (of a ship or plane)
the exponent required to produce a given number
a written record of messages sent or received
a segment of the trunk of a tree when stripped of branches

log (verb)	log up (verb)
enter into a log, as on ships and planes	record a distance travelled; on planes and cars
cut lumber, as in woods and forests