I don't know where you got the etymology from but Etymoline says
of persons, "open to conversation or approach," late 15c., from Old French affable "benign, approachable" (14c.), from Latin affabilis "approachable, courteous, kind, friendly," literally "who can be (easily) spoken to," from affari "to speak to," from ad "to", from PIE root *bha- (2) "to speak, tell, say".
In fact, the meaning I have emphasised was preserved in the modern use of the word:
Cambridge defines affable as meaning
friendly and easy to talk to: She was quite affable at the meeting.
And AHD says
Easy and pleasant to speak to; approachable.
(The same reference to speech is present in ineffable - which cannot be spoken, indescribable)
Amiable is more commonly used than than its other variant, amicable and than affable. Etymoline says about it:
late 14c., "kindly, friendly," also "worthy of love or
admiration," from Old French amiable "pleasant, kind; worthy to
be loved" (12c.), from Late Latin amicabilis "friendly," from Latin
amicus "friend, loved one," noun use of an adjective, "friendly,
loving," from amare "to love".
The form and sense were confused in Old French with amable
"lovable" (from Latin amare "to love"), and by 16c. the English word
also had a secondary sense of "exciting love or delight,"
especially by having an agreeable temper and a kind heart. The word
was subsequently reborrowed by English in Latin form without the sense
contamination as amicable.
Cambridge defines it as
pleasant and friendly
and AHD as
- Friendly and agreeable in disposition; good-natured and likable.
- Cordial; sociable; congenial: an amiable gathering.
There is definitely an overlap between the two in use, they can both mean pleasant and friendly, but these definitions show amiable to describe someone or something that is likable (easy to like), whereas affable someone or something that is approachable (easy to approach or talk to, therefore welcoming).
Having said all that, here is what a native speaker said about this issue on a forum
Affable: I'd use this to describe someone who gets on well with almost anybody. An affable person would most likely be considered kind
and generous by people around them. For me it also carries the nuance
that this person may be outgoing and extroverted as opposed to
reserved and introverted.
Amiable: This word has a kind of flexible nature to it, like pliable or malleable. Maybe it's for this reason that I think of an
amiable person as being someone who gets on well with others because
they are able to look past their faults. There is a very slight
nuance that an amiable person may be taken advantage of because
they try their best to be amiable, as in they try to always be
accommodating to others. An affable person would be more likely to
speak their mind when they think something is off, whereas an
amiable person might stay quiet and just go along with whatever it