“Errer” means “to travel about”, it is derived from “iterare”, which comes form Latin “iter” which means a journey (People reminisce the words itinerary, itinerant).
Synonyms: 1) itinerant, peripatetic, roaming, wandering
2) Mischievous, misbehaving, delinquent
Example: The errant knights in search of adventure met with plenty in their journey.
Example (In the second sense): The errant kids ran away after stealing mangoes from the farm.
Example: When they had ridden a mile or more, Sir Tristram (tristam, tristan comes from sadness) spied a goodly knight before him well armed, who sat by a clear fountain with a strong horse near him, tied to an oak- tree. "Fair sir," said he, when they came near, "ye seem to be a knight errant by your arms and harness, therefore make ready now to joust with one of us, or both."
This is excerpted from the legends of King Arthur and his Knights (which I am currently reading), if you want to read more about him here is the link.
http://en.wikipedia.org/wiki/Tristram
Erratic (Adj): odd, unpredictable
“Errare” means “to wander”, thus something that wanders from normal will be erratic in nature.
Synonyms: aberrant, deviant, capricious, abnormal.
Example: The erratic nature of the pitch made it very difficult for any batsmen to stay at the crease for a long time.
Erroneous (Adj): mistaken, wrong
The word comes from “erron”, which means “a vagabond”; “erron” is derived from “errare” the chief root that links all these words.
Synonyms: amiss, imperfect, inaccurate, flawed, inaccurate.
Example: I would have solved the problem but the data itself was erroneous (A typical engineers dilemma, I must say).
Simple cognates to remember the root errare:
Error
Err
