diff --git a/app/driver/spi.c b/app/driver/spi.c
index 32abf114..811076ab 100644
--- a/app/driver/spi.c
+++ b/app/driver/spi.c
@@ -210,7 +210,7 @@ void spi_mast_blkget(uint8 spi_no, size_t bitlen, uint8 *data)
     os_memcpy((void *)data, (void *)SPI_W0(spi_no), aligned_len);
 }
 
-static uint32 swap_endianess(uint32 n)
+static uint32 swap_endianness(uint32 n)
 {
     return ((n & 0xff) << 24) |
             ((n & 0xff00) << 8) |
@@ -248,10 +248,10 @@ void spi_mast_set_mosi(uint8 spi_no, uint16 offset, uint8 bitlen, uint32 data)
 
     // transfer Wn to buf
     spi_buf.word[1] = READ_PERI_REG(SPI_W0(spi_no) + wn*4);
-    spi_buf.word[1] = swap_endianess(spi_buf.word[1]);
+    spi_buf.word[1] = swap_endianness(spi_buf.word[1]);
     if (wn < 15) {
         spi_buf.word[0] = READ_PERI_REG(SPI_W0(spi_no) + (wn+1)*4);
-        spi_buf.word[0] = swap_endianess(spi_buf.word[0]);
+        spi_buf.word[0] = swap_endianness(spi_buf.word[0]);
     }
 
     shift = 64 - (offset & 0x1f) - bitlen;
@@ -259,9 +259,9 @@ void spi_mast_set_mosi(uint8 spi_no, uint16 offset, uint8 bitlen, uint32 data)
     spi_buf.dword |= (uint64)data << shift;
 
     if (wn < 15) {
-        WRITE_PERI_REG(SPI_W0(spi_no) + (wn+1)*4, swap_endianess(spi_buf.word[0]));
+        WRITE_PERI_REG(SPI_W0(spi_no) + (wn+1)*4, swap_endianness(spi_buf.word[0]));
     }
-    WRITE_PERI_REG(SPI_W0(spi_no) + wn*4, swap_endianess(spi_buf.word[1]));
+    WRITE_PERI_REG(SPI_W0(spi_no) + wn*4, swap_endianness(spi_buf.word[1]));
 
     return;
 }
@@ -293,10 +293,10 @@ uint32 spi_mast_get_miso(uint8 spi_no, uint16 offset, uint8 bitlen)
 
     // transfer Wn to buf
     spi_buf.word[1] = READ_PERI_REG(SPI_W0(spi_no) + wn*4);
-    spi_buf.word[1] = swap_endianess(spi_buf.word[1]);
+    spi_buf.word[1] = swap_endianness(spi_buf.word[1]);
     if (wn < 15) {
         spi_buf.word[0] = READ_PERI_REG(SPI_W0(spi_no) + (wn+1)*4);
-        spi_buf.word[0] = swap_endianess(spi_buf.word[0]);
+        spi_buf.word[0] = swap_endianness(spi_buf.word[0]);
     }
 
     result = (uint32)(spi_buf.dword >> (64 - ((offset & 0x1f) + bitlen)));
diff --git a/app/include/lwip/def.h b/app/include/lwip/def.h
index 46940693..0bb09498 100644
--- a/app/include/lwip/def.h
+++ b/app/include/lwip/def.h
@@ -51,7 +51,7 @@ extern "C" {
  * 'a' is expected to be 'higher' (without overflow) than 'b'. */
 #define LWIP_U32_DIFF(a, b) (((a) >= (b)) ? ((a) - (b)) : (((a) + ((b) ^ 0xFFFFFFFF) + 1)))
 
-/* Endianess-optimized shifting of two u8_t to create one u16_t */
+/* Endianness-optimized shifting of two u8_t to create one u16_t */
 #if BYTE_ORDER == LITTLE_ENDIAN
 #define LWIP_MAKE_U16(a, b) ((a << 8) | b)
 #else
diff --git a/app/lwip/core/ipv4/inet_chksum.c b/app/lwip/core/ipv4/inet_chksum.c
index 99215967..6847fe90 100644
--- a/app/lwip/core/ipv4/inet_chksum.c
+++ b/app/lwip/core/ipv4/inet_chksum.c
@@ -75,7 +75,7 @@
  * @return host order (!) lwip checksum (non-inverted Internet sum)
  *
  * @note accumulator size limits summable length to 64k
- * @note host endianess is irrelevant (p3 RFC1071)
+ * @note host endianness is irrelevant (p3 RFC1071)
  */
 static u16_t ICACHE_FLASH_ATTR
 lwip_standard_chksum(void *dataptr, u16_t len)
diff --git a/app/mbedtls/library/aes.c b/app/mbedtls/library/aes.c
index aff0a993..de0e15ca 100644
--- a/app/mbedtls/library/aes.c
+++ b/app/mbedtls/library/aes.c
@@ -1111,7 +1111,7 @@ int mbedtls_aes_crypt_cbc( mbedtls_aes_context *ctx,
 
 #if defined(MBEDTLS_CIPHER_MODE_XTS)
 
-/* Endianess with 64 bits values */
+/* Endianness with 64 bits values */
 #ifndef GET_UINT64_LE
 #define GET_UINT64_LE(n,b,i)                            \
 {                                                       \
@@ -1147,7 +1147,7 @@ typedef unsigned char mbedtls_be128[16];
  *
  * This function multiplies a field element by x in the polynomial field
  * representation. It uses 64-bit word operations to gain speed but compensates
- * for machine endianess and hence works correctly on both big and little
+ * for machine endianness and hence works correctly on both big and little
  * endian machines.
  */
 static void mbedtls_gf128mul_x_ble( unsigned char r[16],
diff --git a/app/modules/struct.c b/app/modules/struct.c
index 5683222c..99331988 100644
--- a/app/modules/struct.c
+++ b/app/modules/struct.c
@@ -155,7 +155,7 @@ static int gettoalign (size_t len, Header *h, int opt, size_t size) {
 
 
 /*
-** options to control endianess and alignment
+** options to control endianness and alignment
 */
 static void controloptions (lua_State *L, int opt, const char **fmt,
                             Header *h) {