Travail (mochthon). Old word for difficult labour, harder than kopos (toil). In the N.T. only here, 2Th 3:8; 2Co 11:27. Note accusative case here though genitive with mnēmoneuō in 1Th 1:3.
Night and day (nuktos kai hēmeras). Genitive case, both by day and by night, perhaps beginning before dawn and working after dark. So in 1Th 3:10.
That we might not burden any of you (pros to mē epibarēsai tina humōn). Use of pros with the articular infinitive to express purpose (only four times by Paul). The verb epibareō is late, but in the papyri and inscriptions for laying a burden (baros) on (epi̇) one. In N.T. only here and 2Th 3:8; 2Co 2:5. Paul boasted of his financial independence where he was misunderstood as in Thessalonica and Corinth (2 Corinthians 9-12), though he vindicated his right to remuneration.
We preached (ekēruxamen).
We heralded (from kērux, herald) to you, common verb for preach.