Likelier

[lahyk-lee] /ˈlaɪk li/

adjective, likelier, likeliest.
1.
probably or apparently destined (usually followed by an infinitive):
something not likely to happen.
2.
seeming truth, fact, or certainty; reasonably to be believed or expected; believable:
a likely story.
3.
seeming to fulfill requirements or expectations; apparently suitable:
a likely place for a restaurant.
4.
showing promise of achievement or excellence; promising:
a fine, likely young man.
adverb
5.
probably:
We will likely stay home this evening.
/ˈlaɪklɪ/
adjective
1.
(usually foll by an infinitive) tending or inclined; apt: likely to rain
2.
probable: a likely result
3.
believable or feasible; plausible
4.
appropriate for a purpose or activity
5.
having good possibilities of success: a likely candidate
6.
(dialect, mainly US) attractive, agreeable, or enjoyable: her likely ways won her many friends
adverb
7.
probably or presumably
8.
as likely as not, very probably
adj.

c.1300, perhaps from Old Norse likligr “likely,” from likr “like” (see like (adj.)). Old English had cognate geliclic. Meaning “having the appearance of being strong and capable” is from mid-15c., though now mostly confined to American English; according to OED this sense is perhaps influenced by like (v.). Sense of “good-looking” is from late 15c. Meaning “probably” is attested from late 14c., now principally in American English.

LIKELY. That may be liked; that may please; handsome. In the United States, as a colloquial term, respectable; worthy of esteem; sensible.–Worcester. [Bartlett]

As an adverb, late 14c., from the adjective.