Is ἀπόστολος related to ἀποκάλυψις?

[CRMiller]

Are the two words related etymologically?

Are there classical Greek usages of either?

[spiros]

No, ἀπόστολος is from the verb "send" (ἀπό + στέλλω), ἀποκάλυψις is from the verb "cover" (ἀπό + καλύπτω) =  reveal, uncover.

See
ἀπό - Wiktionary
ἀπό - Ancient Greek (LSJ)

[billberg23]

And yes, Herodotus uses both verbs.  Ἀποστέλλω occurs in both Sophocles and Euripides.

[CRMiller]

Thank you both!

Would it be correct to claim that both words refer to knowledge?  ἀπόστολος as sending forth the word (knowledge) and ἀποκάλυψις as an uncovering of knowledge?

Any idea where ἀποκάλυψις appears in Sophocles? I've been searching for leads but not finding any. Fragment?

Thanks again!

[billberg23]

The only thing they have in common is the prefix ἀπο-, which means "from." The verbs ἀποκαλὐπτω and ἀποστέλλω, from which ἀποκάλυψις and ἀπόστολος derive, have nothing semantically to do with one another, nor does either verb imply "knowledge" in classical literature.  Herodotus uses ἀποκαλὐπτω  to mean "uncover" (i.e. a person's head, 1.119), while Plato uses it for uncovering a person's chest (Protagoras 352a).  Again, only ἀποστέλλω (not ἀποκαλὐπτω) occurs in Sophocles, where it signifies sending a person away (Electra 71).  (Cf. also Euripides with this meaning in Medea 281.) 
The noun ἀποκάλυψις is not attested in classical literature until Plutarch, in whom it signifies an "uncovering" of hidden springs (Life of Aemilius Paullus 14.3.1).
Ἀπόστολος, on the other hand, occurs frequently in classical literature, where its usual meaning is "emissary" or "ambassador."