Saṅkappa is an interesting word in Pāli. As part of the NEFP it comes after Right View, usually translation as “Right Intention”. In the suttas its usually synonymous with vitakka-vicāra, and I think “intention” is what is meant by vitakka-vicāra in the Jhānas (specifically the intentions of renunciation, loving-kindness and non-harming). I say intention, but perhaps “resolve” or “plan” is better a translation. Either way, I noticed that the Chāndogyopaniṣad also makes use of Saṅkappa in terms of “intention”. Whilst I realise that Sanskrit is not directly comparable with Pāli, I still thought it was interesting enough to share and perhaps it still can give the word some wider context
saṃkalpo vāva manaso bhūyānyadā vai saṃkalpayate’tha manasyatyatha vācamīrayati tāmu nāmnīrayati nāmni mantrā ekaṃ bhavanti mantreṣu karmāṇi || 7.4.1 ||
tāni ha vā etāni saṃkalpaikāyanāni saṃkalpātmakāni saṃkalpe pratiṣṭhitāni samakḷpatāṃ dyāvāpṛthivī samakalpetāṃ vāyuścākāśaṃ ca samakalpantāpaśca tejaśca teṣāṃ saṃ kḷptyai varṣaṃ saṃkalpate varṣasya saṃkḷptyā annaṃ saṃkalpate’nnasya saṃ kḷptyai prāṇāḥ saṃkalpante prāṇānāṃ saṃ kḷptyai mantrāḥ saṃkalpante mantrāṇāṃ saṃ kḷptyai karmāṇi saṃkalpante karmaṇāṃ saṃkḷptyai lokaḥ saṃkalpate lokasya saṃ kḷptyai sarvaṃ saṃkalpate sa eṣa saṃkalpaḥ saṃkalpamupāssveti || 7.4.2 ||
sa yaḥ saṃkalpaṃ brahmetyupāste saṃkḷptānvai sa lokāndhruvāndhruvaḥ pratiṣṭhitān pratiṣṭhito’vyathamānānavyathamāno’bhisidhyati yāvatsaṃkalpasya gataṃ tatrāsya yathākāmacāro bhavati yaḥ saṃkalpaṃ brahmetyupāste’sti bhagavaḥ saṃkalpādbhūya iti saṃkalpādvāva bhūyo’stīti tanme bhagavānbravītviti || 7.4.3 ||
"Intention, undoubtedly, is greater than the mind, for it is only after a man has formed an intention that he makes up his mind; after that, he vocalizes his speech—and he vocalizes it to articulate a name. The vedic formulas are contained in the name, and rites, in the vedic formulas.
"Now, intention (samkalpa) is the point of convergence of all these things; intention is their essence (atman); and on intention they are based. The earth and the sky were patterned through an intention; wind and space were patterned through an intention; water and fire were patterned through an intention. According to their intention (samklpti) was patterned (samkalpate) rain; according to the intention of rain was patterned food; according to the intention of food were patterned the vital breaths (prana); according to the intention of the vital breaths were patterned the vedic formulas; according to the intention of the vedic formulas were patterned rites; according to the intention of rites was patterned the world; and according to the intention of the world was patterned the Whole. All that is intention! So, venerate intention.
3"If someone venerates brahman as intention—well, himself remaining constant, firmly based, and steadfast, a man wins the worlds patterned after his intention, worlds that are constant, firmly based, and steadfast; and he obtains complete freedom of movement in every place reached by intention, if he venerates brahman as intention."
“Sir, is there anything greater than intention?”
“Yes, there is something greater than intention.”
“Sir, please tell me that.”
The Early Upanishads: Annotated Text and Translation
Also note that here Saṅkappa comes before speech. We see this again in the suttas, where vitakka-vicāra are also required for there to be speech. Here, it looks like the suttas once again have the Chāndogyopaniṣad in mind. Or, perhaps more likely, intention (saṅkappa, vitakka-vicāra) being the pre-requisite for speech was a common idea among the ascetic philosophers at the time.