Emily Dickinson Lexicon

A-LONE', a. [all and one; Germ. allein; D. alleen; Sw. allena; Dan. allene.]

1. Single; solitary; without the presence of another; applied to a person or thing. It is not good that man should be alone. – Gen. ii. [This adjective follows its noun.]
2. It is applied to two or more persons or things, when separate from others, in a place or condition by themselves; without company. And when they were alone, he expounded all things to his disciples. – Mark iv.
3. Only. Thou whose name alone is Jehovah. – Ps. lxxxiii. This sense at first appears to be adverbial, but really is not; whose name single, solitary, without another, is Jehovah. To let alone is to suffer to rest; to forbear molesting or meddling with; to suffer to remain in its present state. Alone, in this phrase, is an adjective, the word to which it refers being omitted; let me alone; let them alone; let it alone; that is, suffer it to be unmolested, or to remain as it is, or let it remain by itself.