Deceitfulness, n.
1. The disposition to deceive; as, a man's deceitfulness may be habitual.
2. The quality of being deceitful; as, the deceitfulness of a man's practices.
3. Tendency to mislead or deceive. "The deceitfulness of riches." Matt. xiii. 22.
Shades of meaning
Fernald has no entry of its own for deceitfulness; he lists it under deception.
He lists it without comment; the entries above explain its neighbors.