Unlimited; not bounded or restricted; undefined. [1913 Webster
"With the auxiliary verbs may, can, must, might, could, would, and should, the simple infinitive is expressed without to; as, you may speak; they must hear, etc. The infinitive usually omits to with the verbs let, dare, do, bid, make, see, hear, need, etc.; as, let me go; you dare not tell; make him work; hear him talk, etc."
" In Anglo-Saxon, the simple infinitive was not preceded by to (the sign of modern simple infinitive), but it had a dative form (sometimes called the gerundial infinitive) which was preceded by to, and was chiefly employed in expressing purpose. See Gerund, 2."
"The gerundial ending (-anne) not only took the same form as the simple infinitive (-an), but it was confounded with the present participle in -ende, or -inde (later -inge)."