The word "skullest" is spelled with the cluster of consonants "ll" which is pronounced as a dark L sound in IPA phonetic transcription. The sound is made by placing the tongue in the middle-back of the roof of the mouth while the back of the tongue is pulled down towards the throat. The vowel sound in "skullest" is spelled with the short U sound, represented in IPA as /ʌ/, which is a mid-central vowel pronounced with a slightly open mouth and the tongue in a neutral position.
The word "skullest" is the second-person singular form of the verb "skull", which is an archaic term meaning "to move fast or glide smoothly".
The etymology of "skull" can be traced back to the Middle English word "skullen" or "scullen", which meant "to listen or pay attention". This Middle English word derived from the Old English word "sculan", meaning "to owe" or "to have an obligation".
Over time, the meaning of "skull" shifted to refer to the movement or gliding of a boat or a bird on the water's surface. The word later became less common in usage, leading to its archaic status in modern English.