The first use of the Greek word "apostle" was in the writings of the ancient Greek orator Demosthenes who lived from 384-322 BCE.
He used it as a naval term to describe an admiral or a fleet or ships sent on a specific mission. Eventually the term APOSTOLOS came to mean a person "sent off" as an envoy for another, like a ship.
It's well-known in the average world that this is what the word means. To illustrate, the Hebrew word, SHALOM which means "peace" also means "welcome." If you notice, in Pete's first post, he quotes that source which comments that the Greek work APOSTOLOS
...is used in a non-technical sense to represent the Heb. שָׁל֥וּחַ
That Hebrew word is a form of the Hebrew word SHALOM:
שׁלום
The previous word looks similar because it is merely the noun in reference to a person, meaning "he who is sent forth to be welcomed." This is why it is in reference to such saintly, peaceful persons.
A footnote to this is that Sodom and Gommorah were destroyed, according to Jewish tradition, because they would not "welcome" those "sent forth." While Christian theology attributed this strictly to homosexuality, Jewish tradition has generally never altered its view that its destruction was due to this particular failure. (Ez 16:49-50) Why such destruction for mere lack of hospitality?
In the Biblical narrative leading up to Sodom's destruction, Abraham had just received divine visitors, one representing God, two others being angelic visitors that went on to Sodom. (Genesis 18) Those two others had been "sent forth," and except for Lot, the rest of the city not merely denied welcoming them but actually tried attacking them in the worst way. (Ge 19:1-9) Jesus would later use this very situation as a condemnation for those who would not accept those that he himself would 'send forth.'
If anyone will not welcome you or listen to your words, shake off the dust from your feet as you leave that house or town. Truly I tell you, it will be more tolerable for the land of Sodom and Gomorrah on the day of judgment than for that town.--Matthew 10:14-15, NRSV.
The term "apostle" is merely a personification of an envoy representing a divine presence. When not accepted, it generally spells doom...or at least, that is how the Biblical narrative plays out.