Common

The common tongue is the English language spoken in many lands in Daventry, according to the Wanderer and Derek Karlavaegen.

Background
It is clear that the Ancient One's language and modern common tongue share the same root, for their writings are directly translatable by simply replacing the appropriate letter of modern alphabet for its corresponding symbol in the ceremonial alphabet. It is probable that the Ancient Ones spoke in the common language and used graphic symbols in their writings as a code for secrecy for for their ceremonial beauty. Or, perhaps, the common "letters" for the spoken language evolved as short-hand notations for the complex symbols used by Ancient Ones.

It is known that the Ancient Ones used two scripts in works; the alphabet of the Ancient Ones which was used primarily for ceremonial purposes, as well as a version of the alphabet in the common tongue of Daventry, a style archaic and fabulously ornate and all run together.

The inscriptions on the Cliffs of Logic use a combination of the ancient symbols as well as riddles in the common alphabet.

Alphabet
The common alphabet includes 26 letters, including;

A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z

These letters sometimes turned into the backwards alphabet cipher to encode messages. In which case Z" becomes "A", "Y" turns into "B," "X" is "C," and so on.

Behind the scenes
The common tongue appears in various ways throughout the King's Quest series. In KQ1 the magic word 'Fill can bee seen at the bottom of the magic clay bowl, it also appears on a letter with the clue to solving the Gnome's backwards name (a name that is based on a backwards version of the English alphabet).

In KQ1, the bowl contains the magic word Fill. The Rumplestiltskin's name is based on an Backwards alphabet cipher.

IN KQ2, the spell word "HOME" can be seen on the amulet.

In KQ3 the English alphabet is seen on the bottle of Saffron, the signs for the Tavern and the Store, and the pages of the The Sorcery of Old in the manual.

In KQ5, the English text can be see on the signs (including the warning sign at the entrance to the Dark Forest, the shops and country inn). and the side of the gypsy wagon.

In KQ6, English text can be seen on the names of the stores, the sentence, the wedding announcement and Alhazred's letter.

In KQ7, English text can be seen on the Danger sign on the elevator, the cover of The Wisdom of Falderal, the box for the weird creature, the settings on the magic scepter, the masks board in the Faux Shop, the text on the base of the statue, the signs on the village buildings, and the note on the door to the Town Hall.