A modern English form of Tessa, a diminutive of Teresa, with a gentle stylized ending.
Tessalee is a modern English form of Tessa, itself a diminutive of Teresa, with a gentle stylized ending. That makes it part of the long history of affectionate name-shortening and later elaboration. It preserves the friendliness of Tessa while giving the name a more expansive and decorative finish.
The result feels soft, feminine, and lightly romantic. Tessalee sounds approachable and cheerful, but the extra syllable and ending make it feel more individualized than the base form alone. This is a common pattern in modern naming: take a known classic, soften it, and then personalize it with a lyrical ending.
Tessalee therefore feels contemporary without losing the warmth of its Teresa family roots. It has a pleasant balance of familiarity and novelty, which is often what gives such names their staying power.