Iranian and Tocharian

During the period of the first centuries BCE, the impact of Iranian becomes important in Tocharian. This is something we know from the relatively large amounts of loanwords in Tocharian from various Iranian languages, beginning with one or several unknown Old Iranian dialects (which are not Avestan or Old Persian) and continuing with loans from various known Middle Iranian languages, such as Khotanese, Sogdian, and Bactrian. As usual with loans, the exact match of the source word is seldom found, meaning that the exact source language cannot be identified.
Iranian loans in Tocharian are interesting from the viewpoint of their semantic domains, which are indicative of the cultural impact of the Iranians on the Tocahrians in Central Asia.

A majority of the words refer to administrative concepts , e.g., titles or specific concepts of merchandise or administration, indicating that the Iranians influenced the Tocharians by imposing an administrative infrastructure. Examples are: Tocharian B waipecce 'possession', from Old lranian, Avestan xʷaēpaiθya­'own' Tocharian B waipte 'separately, apart' < Common Tocharian *wai-pätæ, borrowed probably from an adjective, Old Iranian *hwai­pati in the sense of 'independent, oneself’. Tocharian A pärko, B pärkau 'advantage, profit, interest' < Common Toch. *pärkāwV, borrowed from Old Bactrian, Bactrian φρογαοο 'profit', Old lranian *fragāwa-, Sogdian prγ'w, βry'w, Parthian frg'w 'treasure'. Tocharian A pare, B peri 'debt' < Common Tocharian *pæräī is borrowed from Old Bactrian *pāra > Bactrian paro 'debt, obligation, loan, amount, due'. Tocharian A  āpṣātrik* ‘citizen of a borough or market-town’, borrowed from Old Iranian *αβþαρο < *api-xšaθra- ‘borough, sub-district (of a city)’.  
Other words clearly refer to military concepts, such as values or terms for weapons: Tocharian B tsain 'arrow' from an Old lranian *dzaina-, Avestan zaēna- 'weapon'. Tocharian A āmāṃ B amāṃ ‘pride, arrogance’, loan from Middle Iranian, cf. Buddhist Sogdian ’’m’n ‘power’. Tocharian A āṣāṃ B aṣāṃ ‘worthy’, borrowed from Middle Iranian, cf. Khotanese āṣaṇa- ‘worthy’. Tocharian A āṣānik B āṣānike ‘venerable, worthy of respect’, loan from Middle Iranian, with same sourse as A āṣāṃ B aṣāṃ A senik ‘care, pledge, guaranteee’, from Middle Iranian *zēnik (Khot. ysīnīta, Sogd. zynyh, Kroraina Prakrit jheniya-)  
A bunch of words refer to farming and the household. Examples are: Tocharian AB ās ‘she-goat’, borrowed from Middle Iranian. Tocharian A kātak* B kattāke ‘master of the house, householder’, from Common Tocharian *kāttākǝ borrowed from Middle Iranian, cf. Khotanese ggāṭhaa, itself borrowed from Middle Indic, cf. Gāndhārī Prakrit *ghahaṭha, from Sanskrit gṛhastha-. Tocharian A miṣi B miṣṣe, miṣṣi ‘field’, borrowed from Khotanese mäṣṣa, miṣṣa ‘field for seed’.  
 A small amount of words are Buddhist terms (normally, the impact of Sanskrit is enormous on both Tocharian languages here). Examples are: Tocharian A pissaṅk ‘community of monks’, from Middle Iranian from Skt. bhikṣusaṃgha-  ‘Mönchsgemeinde, Mönchsorden’ (SWTF III:298b), cf. Khotanese bisaṃga-.  
Finally, we have a group of words referring to plants and ingrediants which are unfamiliar to the Tocharian fauna (also here, Sanskrit loans are much more common). Examples are: Tocharian A kārāś B karāśe* Via TB from Khotanese karāśśa ‘climbing plant’. Tocharian A kuñcit B kwäñcit, kuñcit, from Khotanese kuṃjsata- ‘sesame’.
In conclusion, the Iranian impact on Tocharian is mainly pre-Buddhist, referring to concepts of administration, warfare, and farming. With the change to Buddhism, the impact of Old and Middle Aryan becomes completely dominating in both Tocharian languages.
 
The words have been extracted from these sources:
Carling Gerd (to appear). A Dictionary and Thesaurus of Tocharian A. Complete Edition. In collaboration with Georges-Jean Pinault. Wiesbaden: Harrassowitz (610p.).
Carling, Gerd (2005). Proto-Tocharian, Common Tocharian, and Tocharian – on the value of linguistic connections in a reconstructed language. In: Jones-Bley, Karlene, Huld, Martin E., Volpe, Angela Vella,  Dexter, Miriam Robbins Proceedings of the Sixteenth Annual UCLA Indo-European Conference. Journal of Indo-European Studies. Monograph Series 50, 47-70.
 
These sources have many references to works by, e.g., Georges-Jean Pinault, K T Schmidt, Werner Winter, Nicholas Sims-Williams, Harold Bailey, L Isebaert, Jörundur Hilmarsson.