e.g from what I know, the Pomeg Berry comes from the fruit pomegranate
Unsurprisingly, they're (almost) all puns on fruits and vegetables:
Cheri - Cherry Chesto - Chestnut Pecha - Peach Rawst - Strawberry Aspear - Asian pear Leppa - Apple Oran - Orange Persim - Persimmon Lum - Plum Sitrus - Citrus Figy - Fig Wiki - Kiwi Mago - Mango Aguav - Guava Iapapa - Papaya Razz - Raspberry Bluck - Blackberry Nanab - Banana Wepear - Western pear Pinap - Pineapple Pomeg - Pomegranate Kelpsy - Kelp Qualot - Loquat Hondew - Honeydew Grepa - Grape Tamato - Tomato Cornn - Corn Magost - Mangosteen Rabuta - Bulbapedia says rambutan, but it may also come from rutabaga Nomel - Lemon Spelon - Spiked melon Pamtre - Palm tree Watmel - Watermelon Durin - Durian Belue - Blueberry Occa - Cacao / cocoa Passho - Passiflora / passion fruit Wacan - Wax candle, referencing the Japanese name, where it's named after a "candle tree" Rindo - Tamarind Yache - Cherimoya Chople - the Thai fruit chmphū̀ and wax apple Kebia - Akebia Shuca - Cashew Coba - Babaco Payapa - Papaya Tanga - Pitanga Charti - Chinese artichoke Kasib - the Japanese fruit busshukan, known colloquially as "Buddha's Hand" Haban - teriha-banjirō, Japanese for strawberry guava Colbur - Cocklebur Babiri - Biriba Roseli - Roselle Chilan - "Chinese lantern" is a nickname for the fruit Physalis alkekengi Liechi - Lychee Ganlon - Longan Salac - Salak Petaya - Pitaya Apicot - Apricot Lansat - Langsat Starf - Starfruit Enigma - Enigma Micle - Miracle fruit Custap - Custard apple Jaboca - Jabuticaba Rowap - Rose apple and water apple Kee - Ackee Maranga - Marang Nutpea - Peanut
Source: Each berry's Bulbapedia page has etymology at the end