Common epithets (or adjectives) applied to Poseidon are Enosichthon (Ἐνοσίχθων) "Earth Shaker" or "earth-shaking" and Ennosigaios (Ἐννοσίγαιος), used by Homer in the Iliad and by Nonnus in Dionysiaca.

Of the two phrases, Enosichthon has an older evidence of use, as it is identified in Linear B, as 𐀁𐀚𐀯𐀅𐀃𐀚, E-ne-si-da-o-ne,
The epithets Ennosigaios (and Ennosidas),  Gaiēochos (Γαιήοχος) ,Seisichthon ,  ,indicate the chthonic nature of Poseidon.
In the town of Aegae in Euboea, he was known as Poseidon Aegaeus and had a magnificent temple upon a hill, Epithets like Pelagios (Πελάγιος) "belonging to the sea" in Ionia, Phykios (φύκιος) "full of seaweed" in Mykonos , "Kyanochetis" ,(κυανοχαίτης: "Dark-Haired", dark blue of the sea), indicate that Poseidon was regarded as holding sway over land as well as the sea.

Poseidon also had a close association with horses, known under the epithet  Hippios(ἲππειος), usually in Arcadia.
He is more often regarded as the tamer of horses, but in some myths he is their father, either by spilling his seed upon a rock or by mating with a creature who then gave birth to the first horse.
He was closely related with the springs, and with the strike of his trident, he created springs.
Many springs like Hippocrene and Aganippe in Helikon are related with the word horse (hippos). (
also Glukippe, Hyperippe).

Some other epithets of Poseidon are:
"Asphaleios", (ασφάλεια: safety), as protector from the earthquakes.

"Helikonios", (Ελικώνιος) related with the mountain Helikon.

"Tavreios", (Ταύρειος: related with the bull).
There was a fest "Tavreia" in Ephesos.

"Petraios" ((Πετραἵος): related with rocks) in Thessaly.
He hit a rock, and the horse "Skyphios" appeared.

"Ptortheion" (Πτορθείων) "promotor of vegetation".

"Epoptis" (επόπτης: supervisor) in Megalopolis
"Phykios" (Φύκιος: related with seaweeds) in Mykonos.

"Phytalmios" (Φυτάλμιος) related with the vegetation in Troizen, Megara, Rhodes.

Epithets related with the genealogy trees: "Patrigenios", "Genethlios", "Genesios", "Pater", "Phratrios".

"Epactaeus", meaning "god worshipped on the coast", in Samos.
Common epithets (or adjectives) applied to Poseidon are Enosichthon (Ἐνοσίχθων) "Earth Shaker" or "earth-shaking" and Ennosigaios (Ἐννοσίγαιος), used by Homer in the Iliad and by Nonnus in Dionysiaca. 
Of the two phrases, Enosichthon has an older evidence of use, as it is identified in Linear B, as 𐀁𐀚𐀯𐀅𐀃𐀚, E-ne-si-da-o-ne,
The epithets Ennosigaios (and Ennosidas),  Gaiēochos (Γαιήοχος) ,Seisichthon ,  ,indicate the chthonic nature of Poseidon. In the town of Aegae in Euboea, he was known as Poseidon Aegaeus and had a magnificent temple upon a hill, Epithets like Pelagios (Πελάγιος) "belonging to the sea" in Ionia, Phykios (φύκιος) "full of seaweed" in Mykonos , "Kyanochetis" ,(κυανοχαίτης: "Dark-Haired", dark blue of the sea), indicate that Poseidon was regarded as holding sway over land as well as the sea. 
Poseidon also had a close association with horses, known under the epithet  Hippios(ἲππειος), usually in Arcadia. He is more often regarded as the tamer of horses, but in some myths he is their father, either by spilling his seed upon a rock or by mating with a creature who then gave birth to the first horse. He was closely related with the springs, and with the strike of his trident, he created springs. Many springs like Hippocrene and Aganippe in Helikon are related with the word horse (hippos). (also Glukippe, Hyperippe).
Some other epithets of Poseidon are:
"Asphaleios", (ασφάλεια: safety), as protector from the earthquakes.
"Helikonios", (Ελικώνιος) related with the mountain Helikon.
"Tavreios", (Ταύρειος: related with the bull). There was a fest "Tavreia" in Ephesos.
"Petraios" ((Πετραἵος): related with rocks) in Thessaly. He hit a rock, and the horse "Skyphios" appeared.
"Ptortheion" (Πτορθείων) "promotor of vegetation".
"Epoptis" (επόπτης: supervisor) in Megalopolis
"Phykios" (Φύκιος: related with seaweeds) in Mykonos.
"Phytalmios" (Φυτάλμιος) related with the vegetation in Troizen, Megara, Rhodes.
Epithets related with the genealogy trees: "Patrigenios", "Genethlios", "Genesios", "Pater", "Phratrios".
"Epactaeus", meaning "god worshipped on the coast", in Samos.
Poseidon